Knee Osteoarthritis Associated With Distinct Depression Subtypes

The anhedonic and melancholic subtypes may be risk factors for increased pain and disability in knee OA.

Individuals with symptomatic knee osteoarthritis (OA) and those at risk for knee OA had 4 distinct depression subtypes, each with differentiating characteristic symptoms that affected pain and disability over 4 years, according to a study published in Arthritis Care & Research.

As OA worsens, psychiatric comorbidities, including depressive symptoms, may develop, which could potentially affect OA progression and increase pain and disability. However, depression in OA remains underrecognized, and the heterogeneity of depressive symptomatology and its effect on patients with OA is poorly understood, with few studies examining depression in this population. Investigators sought to describe OA-related depression subtypes and explore their effects on patient pain and disability.

The Osteoarthritis Initiative — an observational cohort study examining knee OA biomarkers and risk factors — enrolled a total of 4486 participants and divided them into those with (n=1626) or those at risk for (n=2860) symptomatic knee OA. At baseline, patients were rated for depressive symptoms using the 20-item Center for Epidemiologic Studies Depression scale, with latent class analysis modeling characterizing depression as 1 of 4 depression subtypes.

The primary outcomes were the pain and disability subscales of the Western Ontario and McMaster Universities Arthritis Index (WOMAC), assessed at baseline and annually through 4 years of follow-up. The relationships between WOMAC subscores and depression subtypes were calculated using weighted estimating equations, and results were stratified according to baseline OA status (“with” vs “at risk”).

Using the asymptomatic group as a reference for comparison, over 4 years, researchers observed detectable mean differences on the WOMAC pain and disability subscales in the anhedonic (1.5-2.3 WOMAC units) and melancholic (4.8-6.6 WOMAC units) groups, but not the catatonic group. These results indicated that anhedonic or melancholic depression may represent OA pain and disability risk factors. When stratified by OA status, there were typically greater associations between WOMAC subscores and depression subtypes in those with vs at risk for symptomatic knee OA.

Study strengths included being among the largest latent class analysis studies on depression subtypes in musculoskeletal conditions, use of statistical techniques to overcome incorrect modeling specification on confounder adjustment, and use of a well-documented and comprehensive cohort.

Study limitations included a lack of atypical or psychotic depression subtype symptom assessment, use of a 3-step design that may increase misclassification, and potential unmeasured confounding.

“Ultimately, findings highlight the difficulty of using standard depression treatments in individuals with musculoskeletal disorders, and protocols that address the specific symptomatology of different subtypes of depression that may present in knee OA patients are needed,” concluded the authors.